It's like a game show!

I have been getting a ....Ping.... i found out it is coming from my downpipe it make a ping noise even when i shut the car off. the first i heard of it, i was at a stop light. it's not a steady ping at all what i mean by that is that i have tried to time it and it's irregular.

 

It's probably just things (heat shields, etc.) expanding/contracitng with heat. Lots of cars make similar noises, especially while they are cooling down.

 

Do you have the Monty Python mod?